Recently, broadcast services having high definition (HD) resolution have expanded nationwide and worldwide, and thus, many users are accustomed to high-resolution and high quality images. Therefore, many organizations have striven to develop next generation image devices. In addition, since the interest in HDTV and ultra high definition (UHD) having resolution four times higher than that of HDTV has increased, there is a need for higher resolution and a compression technology for high-definition images.
Image compression technology includes various techniques, such as an inter-prediction technique of predicting pixel values included in a current picture from previous or subsequent pictures of the current picture, an intra-prediction technique of predicting pixel values included in a current picture using pixel information in the current picture, a transform and quantization technique of compressing energy of a residual signal, and an entropy encoding technique of assigning a short code to a value with a high appearance frequency and assigning a long code to a value with a low appearance frequency. Image data may be effectively compressed by using such image compression technology, and may be transmitted or stored.
In conventional video encoding/decoding, when performing prediction on a current encoding/decoding target block, the number of alternative reference blocks is limited, such that it is difficult to enhance encoding/decoding efficiency of inter prediction.